In recent years, flat panel displays are required to have a large size, high image quality and low power consumption. Under the circumstances, high-image quality organic EL displays, which can be driven at a low voltage, are attracting great attention. Full-color active matrix type organic EL displays, for example, are provided with a thin film-like organic EL element on a substrate having a TFT (thin film transistor). In the organic EL element, organic EL layers including red (R), green (G) and blue (B) light emitting layers are laminated between a pair of electrodes. The TFT is connected to one of the pair of electrodes. Then, voltage is applied across the pair of electrodes so as to cause each light emitting layer to emit light, whereby an image is displayed.
In order to manufacture an organic EL element, it is necessary to form light emitting layers made of organic light emitting materials that emit respective colors in a predetermined pattern.
Known methods for forming light emitting layers in a predetermined pattern are vacuum vapor deposition method, inkjet method and laser transfer method. For example, the vacuum vapor deposition method is often used for low molecular organic EL displays (OLEDs).
In the vacuum vapor deposition method, a mask (also called a “shadow mask”) having a predetermined pattern of opening s is used. The deposition surface of a substrate having the mask closely fixed thereto is disposed so as to oppose a vapor deposition source. Then, vapor deposition particles (film forming material) from the vapor deposition source are deposited onto the deposition surface through the opening s of the mask, whereby a predetermined pattern of thin films is formed. Vapor deposition is performed for each color of the light emitting layers, which is referred to as “vapor deposition by color”.
For example, Patent Documents 1 and 2 disclose a method for performing vapor deposition by color in which light emitting layers for respective colors are formed by sequentially moving a mask with respect to a substrate. With such a method, a mask having a size equal to that of a substrate is used, and the mask is fixed so as to cover the deposition surface of the substrate at the time of vapor deposition.